1. Technical Field
The present invention relates to a semiconductor laser, a light source device using the semiconductor laser, a lighting device using the light source device, a projector, and a monitor device.
2. Related Art
In the past, an ultra high-pressure mercury lamp (UHP) has been commonly used for a projector for projecting an image as a light source thereof. However, the UMP has various problems such that it takes time as long as several minutes before the maximum luminance has been reached, and consequently, instant lighting is difficult, that it has relatively short life, or that the color reproduction range is not sufficiently large. Therefore, in recent years, development of a method of using semiconductor lasers as the light source has been in progress (see e.g., JP-A-2006-106130).
In the semiconductor lasers, by applying drive voltage to a laser diode (a laser emitting element) forming the semiconductor laser so that a drive current having a current value greater than the laser oscillation start current flows, the laser diode starts the laser oscillation, thus emitting the laser beam. It should be note that in view of providing a longer operating life, it is not preferable to apply a direct current drive voltage to the laser diode. Therefore, a pulsed drive voltage is commonly applied to the laser diode to make a pulsed drive current flow therethrough, thus making it operate to emit a laser beam. Hereinafter this operation is referred to as “pulse drive.”
However, there is a problem that when the pulse drive is executed on the laser diode, a flyback voltage with opposite polarity to the drive voltage should be applied to the laser diode by the stray inductance existing owing to the mounting of the circuit composing the light source device, resulting in the degradation of the operation efficiency of the circuit for driving the laser diode.